tree 45a86142fb457318c12b712e4dcb3a19552577cb
parent 424baff549a9c8a7b5e814ce2bcb857d25163468
author Alexey Kardashevskiy <aik@ozlabs.ru> 1404199827 +1000
committer Paolo Bonzini <pbonzini@redhat.com> 1404203788 +0200

configure: Fix -lm test, so that tools can be compiled on hosts that require -lm

The existing test whether "-lm" needs to be included or not is
insufficient as it reports false negative on Fedora20/ppc64.
This happens because sin(0.0) is a constant value which compiler
can safely throw away and therefore there is no need to add "-lm".
As the result, qemu-nbd/qemu-io/qemu-img tools cannot compile.

This adds a global variable and uses it in the test to prevent
from optimization.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[Use Peter's improvement on the test to fool LTO, and remove the
 now useless -lm addition in Makefile.target. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>